"'Assuming individuals receive some finite, above zero amount of utility per unit time, living forever would give infinitely >more utility than living for a finite amount of time.'

Only if the utility per unit time is constant. " You're right. Edited.

Most useful things are subject to diminishing returns. Why should lifespan be an exception? I could even easily imagine that at a certain point, utility turns negative.

Do you ever get bored, or find yourself at a loose end? Do you think that would happen more or less often if your >lifespan were longer? I think it would happen much less, if at all, if lifespan was longer, as in the future, one could potentially cure boredom, as preventing boredom sounds much easier than living forever.

Human lifespan (and health in old age) has increased considerably over the last 100 years in the Western world, and >that increased lifespan has largely been spent in retirement. Consider how retired people typically spend their time, >and ask yourself whether that lifestyle strikes you as appealing. Taking the outside view, why do you think you would >use your increased lifespan in any more productive a manner? As far as I know, the elderly are unproductive because agings has degraded their physical and mental abilities so far that they are no longer very useful in the work force. This wouldn't happen if aging was cured. Regardless, one wouldn't need to be productive one AGI's created.

I highly suggest reading the fun theory sequence.